All of our processes contain variation. Understanding variation is vital when deciding how to improve our processes and services.

David Williams

Variation is the natural fluctuation that we see in our processes. For example, the number of times the phone rings at work a day is never constant. The differing number of times it rings a day is the variation we see in this process.There are two different types of variation, “common cause” variation and “special cause” variation.

An example of how variation works…

Every day I drive to work. It normally takes me about 55 minutes, if there are no unusual occurrences, but this does vary. It rarely takes exactly the same time to drive to work due to levels of traffic, weather, or the timing of traffic signals. These time differences are expected. It is common cause variation.

One day, there was an accident on the Motorway. My journey to work took 94 minutes. This is special cause variation. If this happened to you, would you change your route to work every other day just because of this single occurrence?